The invention described herein may be manufactured and used by and for the Government of the United States of America for Governmental purposes without the payment of any royalties thereon or therefor.
1. Field of the Invention
The present invention relates to antennas and more particularly to box antennas.
2. Brief Description of Prior Developments
The prior art describes various types of box antennas. U.S. Pat. No. 6,034,644 to Okabe et al, for example, discloses a coaxial resonant slot antenna which includes a flat rectangular conductive box hanging its top plate with a slot being defined therein. A strip conductor is disposed inside the box and electrically insulated from the box while high frequency or RF power is fed to the strip. An island conductor is provided in the slot for defining a capacitance between itself and the frame. This capacitance is rendered variable in value by use of a variable circuit.
U.S. Pat. No. 6,307,520 to Liu discloses a boxed-in slot antenna which is provided with a conductive box, functioning as a waveguide, which is configured substantially parallel to the ground plane in which the slot is formed, thereby providing significant space savings relative to prior art designs wherein the box is positioned perpendicular to the conductive ground plane. The antenna is constructed using printed circuit board technology, by forming the ground plane as a coating on one side of a printed circuit board substrate, forming the main conductive plane of the conductive box structure on the other side of the printed circuit board, and interconnecting the two using plated through holes. The folded structure of the conductive box is reported to be suited for space-critical applications, such as may be found in laptop computers and other portable and handheld electronic devices, when it is desired to interconnect with a wireless local area network.
A need still exists, however, for a further improved box antenna which simultaneously allows for circular polarization in an inexpensive, compact, and broad band configuration.
The present invention is a dual uncoupled mode box antenna which includes a conductive bottom horizontal ground plane. In this antenna there is a box structure superimposed on this ground plane. The box structure includes a vertical first conductive side insulated from the ground plane, and a vertical second conductive side insulated from the ground plane positioned in gapped relation to the first side. There is also a vertical third conductive side which is grounded to the ground plane and which is positioned in perpendicular gapped relation to the second side. A vertical fourth conductive side is also grounded to the ground plane and is positioned in perpendicular gapped relation to the first and third sides. A conductive top is superimposed over and insulated from the first, second, third, and fourth sides. The first and second sides are fed in quadrature to create either left handed or right handed polarization.